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This invention relates to a miniaturized, programmable radiation source for use in delivering substantially constant or intermittent levels of x-rays to a specified region and, more particularly, to an apparatus for delivering a controlled dose of radiation to a localized volume of tissue, such as a volume of tissue of the human body.
In the field of medicine, radiation is used for diagnostic, therapeutic and palliative treatment of patients. The conventional medical radiation sources used for these treatments include large fixed position machines such as linear accelerators (xe2x80x9cLINACsxe2x80x9d), smaller transportable radiation delivery machines such as high-dose-rate after loaders, and catheters for low-dose-rate brachytherapy. The current state of the art treatment systems utilize computers to generate complex treatment plans for treating complex geometric volumes.
Typically, these systems apply doses of radiation in order to inhibit the growth of new tissue because it is known that radiation affects dividing cells more than the mature cells found in non-growing tissue. Thus, the regrowth of cancerous tissue in the site of an excised tumor can be treated with radiation to prevent the recurrence of cancer. Alternatively, radiation can be applied to other areas of the body to inhibit tissue growth, for example the growth of new blood vessels inside the eye that can cause macular degeneration.
Conventional radiation treatment systems, such as the LINAC used for medical treatment, utilize a high power remote radiation source and direct a beam of radiation at a target volume, such as a tumor inside the body of a patient. This type of treatment is referred to as teletherapy because the radiation source is located a predefined distance, typically on the order of one meter, from the target. This treatment suffers from the disadvantage that tissue disposed between the radiation source and the target is exposed to radiation.
An alternative treatment system utilizing a point source of radiation is disclosed in U.S. Pat. No. 5,153,900 issued to Nomikos et al., owned by the assignee of the present application, which is hereby incorporated by reference. The system includes a miniaturized, insertable probe capable of producing low power radiation in predefined dose geometries or profiles disposed about a predetermined location. One advantage of this system is that the radiation is applied to treat a predefined tissue volume, without significantly affecting the tissue in adjacent volumes.
A typical use of the described radiation therapy system involves positioning the insertable probe into the tumor or the site where the tumor or a portion of the tumor was removed to treat the tissue adjacent the site with radiation. In order to facilitate controlled treatment of the site, it is desirable to support the tissue portions to be treated at a predefined distance from the radiation source. Alternatively, where the treatment involves the treatment of surface tissue or the surface of an organ, it is desirable to control the shape of the surface as well as the shape of the radiation field applied to the surface.
The treatment can involve the application of radiation, either continuously or intermittently, over an extended period of time. Therefore, it is desirable that the insertable probe be adjustably supported in a compliant manner to accurately position the radiation source with respect to the treated site and accommodate normal minor movements of the patient, such as movements associated with breathing.
Accordingly, it is an object of the present invention to provide an improved system for delivering radiation to a localized region.
The present invention is directed to a radiation applicator system which is mountable to a radiation source in order to apply a predefined dose of radiation to a surface of a body to treat a volume of tissue. The radiation applicator system includes an applicator and, preferably, an adapter. When included, the adapter couples the applicator to a radiation source. The applicator includes an applicator shank and an applicator head. The adapter may take any of a variety of forms, and may, for example, be integral with the shank, the radiation source, or may include one or more separate components which couple the shank to the radiation source. The adapter may also be formed from some combination thereof. In the preferred form, the adapter is a separate component that engages the applicator shank at the shank""s proximate end and thereby allows coupling of the applicator to the radiation source, when the adapter is coupled to the radiation source. At the opposite and distal end of the applicator shank is the applicator head, having a convex treatment surface adapted for applying a predefined dose of radiation across a surface contour to treat a predefined volume of tissue surrounding a surgical site. Preferably, the applicator head and surface contour coincide such that the convex surface of the applicator head engages and supports the concave surface of the volume to be treated and applies a predetermined dose of radiation across the surface to that volume.
In one embodiment, the radiation source includes an elongated probe and is adapted for producing a predefined radiation dose profile about a predetermined location with respect to the probe. In this embodiment, the applicator system can also include a low energy radiation filter adapted to surround at least a portion of the probe within the applicator head. The low energy radiation filter serves to reduce the low energy radiation produced by the probe which can damage tissue adjacent to the applicator head. The applicator head engages the area to be treated, such as the area adjacent to the site where a tumor was removed in order to permit the application of radiation to prevent the regrowth of the tumor.
Preferably, the applicator system is adapted to be mounted to the radiation source and encase the source""s elongated probe to form a self-contained treatment assembly or kit. During a surgical procedure, the treatment assembly, including the applicator system and the radiation source, can be supported by a carrier system. The carrier support system can be adapted to support the treatment assembly in a substantially weightless configuration in order to facilitate positioning by the physician during surgery and to accommodate substantially minor movements by the patient, such as those caused by breathing.